The described invention relates in general to integrally bladed rotors for use in gas turbine engines, and more specifically to a method for preparing a BLING rotor that incorporates at least one metal matrix composite into the ring component of the rotor or the airfoil component of the rotor.
Rotors, such as those used with gas turbine engines typically include a basic rotor body and a plurality of rotor blades attached thereto. Rotor blades may be anchored in specific recesses formed in the rotor body or the rotor blades may be formed integrally with the rotor body itself. Integrally bladed rotors are referred to as BLISKS (bladed disc) if a disc-shaped basic rotor body is utilized or a BLING (bladed ring) if a ring-shaped basic rotor body is utilized. BLING rotors offer distinct advantages over BLISK rotors because the BLING design results in a larger internal cavity than is typically possible with the BLISK design. This cavity provides space within the engine that may be used for additional equipment such as, for example, an embedded electric generator and/or heat exchanger. The BLING design may also provide improved rotor dynamic damping and higher E/rho (by as much as 70%), compared to conventional metal disks, and even to integrally bladed BLISK rotors. The BLING design also enables the use of metal matrix composite (MMC) for the basic rotor body. In the context of gas turbine engines, high strength, low density MMC may offer significant advantages over monolithic metal alloys, including a significant decrease in the weight of engine components.
Known methods for manufacturing MMC reinforced BLING rotors typically utilize hot isostatic pressing (HIP), which includes diffusion bonding of various components. The HIP process consolidates metal matrix composites into higher density, uniform, fine grain structures. However, incorporating an MMC ring into a multi-load path structure, i.e., rotor to blade, is technically challenging and requires a large number of process controls to ensure that no internal defects are present after the structure has been created. A thermal expansion coefficient mismatch between the MMC ring and monolithic material used for the blades may produce a residual compressive stress field along the bonding surface. Resultant internal defects are not detectable using non-destructive inspection techniques; thus, strict process controls must be implemented. Consequently, the expense involved in creating a BLING rotor of suitable quality using MMC and HIP diffusion bonding may be considerable compared to the cost of a BLISK rotor machined from a conventional forging.
Thus, there is a need for a reliable, economically-sound method for manufacturing BLING rotors that incorporate MMC, wherein the completed rotor may be treated to relieve residual compressive stress, and wherein bond surface integrity can be inspected using conventional, non-destructive methods for detecting internal defects.